Lower Extremity Somatosensory Function Throughout Concussion Recovery: A Prospective Cohort Study

Objective:Balance impairments may suggest somatosensory disruption beyond concussion clinical recovery, but somatosensory subsystems have never been directly assessed. Our objective was to examine somatosensory function between individuals with a concussion and healthy matched-controls at acute (<7 days) and asymptomatic (<72 hours of being symptom-free) time points. Setting:Laboratory. Participants:Participants with a concussion and matched controls (n = 24; 58% male, age: 19.3 +/- 1.1 years, mass: 70.3 +/- 16.4 kg, height: 177.3 +/- 12.7 cm). Design:Prospective cohort. Main Measures:Somatosensory assessments on the dominant limb at both time points included: (1) plantar touch sensation threshold via Semmes-Weinstein monofilaments, (2) plantar pressure pain threshold via algometry, and (3) knee absolute passive joint repositioning (PJR) error via Biodex across 3 arcs (105 degrees-75 degrees, 30 degrees-60 degrees, 90 degrees-45 degrees knee-flexion). We used mixed-model analyses of variance, post hoc Tukey honestly significant difference t tests with mean difference, 95% CI, and Hedges' g effect sizes to examine outcomes. Results:Touch sensation had a group effect with the concussion cohort needing 0.95 grams of force (gf) more relative to controls (95% CI: 0.03 to 1.87; P = .043). No touch sensation interaction was present, but medium and large effects were observed for greater gf needed among the concussed cohort at the acute (1.11 gf; 95% CI: 0.17 to 2.05; g = 0.96) and asymptomatic time points (0.79 gf; 95% CI: -0.15 to 1.73; g = 0.73). No plantar pressure pain threshold effects were observed (P >= .311), with negligible pressure difference magnitudes at the acute (0.26 pound force [lbf]/cm(2); 95% CI: -1.54 to 2.06; g = 0.13) and medium magnitudes at the asymptomatic time points (0.99 lbf/cm(2); 95% CI: -0.81 to 2.80; g = 0.42) for the concussed cohort needing more pressure to detect pain. The 30 degrees to 60 degrees PJR had a time effect, with asymptomatic time point having 3.12 degrees better accuracy (95% CI: 1.23 degrees to 5.02; P = .002). The concussed cohort had small-to-medium magnitude differences relative to controls at the acute time point for PJR during 105 degrees to 75 degrees (0.89 degrees; g = 0.30) and 90 degrees to 45 degrees (0.62 degrees; g = 0.17), but not 30 degrees to 60 degrees (-1.75 degrees; g = -0.40). Conclusions:Individuals with a concussion exhibited large effects for diminished plantar touch sensation and small to medium effects for inhibited plantar pressure pain sensation compared with controls, which may indicate altered somatosensory function. Negligible PJR differences suggest knee joint position sense is not altered post-concussion. Pre- and postconcussion examination is warranted to understand causal somatosensory mechanisms.

Automated summary

The study aimed to examine somatosensory function in individuals with a concussion compared to healthy controls. The results showed that individuals with a concussion had differences in plantar touch sensation and plantar pressure pain sensation compared to controls, but no significant differences in knee joint position sense.